The term “fiber” covers a very broad range of natural and man-made materials. Once again, only the most common fibers used in sealing devices are reviewed in this course; they are listed alphabetically by generic name.



  • Man-made organic fiber
  • Introduced by DuPont under the trade name KEVLAR® in the early 1970s
  • Good wear resistance
  • Good thermal and electrical insulation properties
  • Very high tensile strength, high modulus, and low density
  • Starts degrading between 500°F (260°C) and 600 °F (315°C) with very little aramid left at 800°F (425°C)
  • Attacked by concentrated hot acids or caustics



  • Rod-like fibers of various diameters and lengths
  • Produced by pyrolysis (heat treatment process) to various levels of carbon content materials (I.E. rayon, acrylonitriles, pitch, etc.)
  • Good heat and chemical resistance



  • Natural fibers; most common: cotton and so-called “vegetable” fibers
  • Readily available in huge quantities; low price
  • Moderate chemical and general fluid resistance
  • Not generally recommended for use over 250°F (121°C)



  • Excellent heat resistance and incombustible
  • Begins to degrade at approximately 750°F (399°C)
  • Does not absorb moisture; will not rot or decay
  • Resistant to acids, oils, many solvents, weather, and corrosive vapors
  • Electrical insulator
  • Used in combination with aramid fiber to reinforce Garlock expansion joints



  • Rod-like fibers of various diameters and lengths
  • Produced by special heat treatment of carbon fibers at approximately 5072°F (2800°C)
  • Excellent heat and chemical resistance
  • Versatile; popularity in the gasketing industry continues to grow



  • Fibers are amorphous and highly homogenous because of their metamorphosis from volcanic rock
  • Do not burn; chemically inert
  • Resistant to high temperatures; above 930°F (500°C)



Tire Cord (expansion joints)

  • Man-made polyamide with high tensile strength and good ultimate elongation properties
  • Good resistance to common solvents, fuels, oils, and greases
  • Attacked by strong alkalines (caustics) and acids, oxidizing agents, phenol, and formic acid
  • Temperature limit: 250°F (121°C)



  • High quality, synthetic material
  • In spun form, polyester has a very high density and thread count, making it resistant to permeation
  • Polyester cloth is considered the standard reinforcement material in Garlock expansion joints